1. Field of the Invention
The present invention relates to a power supply system with heterogeneous multiple inputs, i.e. connected in input to a plurality of electrical power grids delivering direct or alternating current.
More particularly, the invention relates to a power supply system adapted to be connected in input to N distinct power grids delivering a direct or alternating input voltage and to deliver a direct distribution voltage, N being an integer greater than or equal to 2, comprising:                a distribution bus operating under the distribution voltage,        N unidirectional converters that can respectively be connected in input to a given power grid and able to deliver an electrical power to the distribution bus, and        control means capable of controlling the unidirectional converters.        
This type of power supply is particularly used in aeronautics, and is designed to provide regulated voltage to the onboard electronic circuits of an aircraft.
These power supplies are thus subject to a number of specific constraints.
For example, they must be able to switch from a priority power supply grid to a redundant power supply grid in a secured manner—i.e. while avoiding any exchange of energy between said grids—, with well-controlled transitional phases without oscillations in the context of increasing the dynamics and impedance of those power supply grids. The withdrawal of power from grids other than the priority grid must also be minimized.
Furthermore, they must make it possible to withdraw a normal-operation voltage on each of the redundant power supply grids to power auxiliary electronic equipment.
These power supply systems must also make it possible to withstand power line disturbances occurring on the selected power supply grid and allow filtering of inrush currents coming from the downstream electronic equipment.
Lastly, they must be able to operate from power supply grids delivering electrical power supplies having very different formats, for example whereof the supplied current is direct for some and alternating for others, whereof the voltage and/or frequency is different, and which are not connected to a same ground potential.
2. Description of the Related Art
FR 2 815 789 describes a power supply system of the aforementioned type capable of selecting a power supply grid from among a plurality of power supply grids. The switching logic between the power supply grids is rigid and implemented by a dedicated control member capable of ordering opening or closing of the contacts of a diode switch as a function of the voltage delivered by each of the converters.
US 2005/134239 also describes a power supply system of the aforementioned type. In that document, various topologies are considered, in which direct or alternating voltages delivered by distinct power supply grids are combined in order to supply a load situated downstream of the power supply system.
However, these solutions are not fully satisfactory.
In fact, in the current context of increasing dynamics of the power supply grids, the rigidity of the switching logic of the power supply system described in the first document involves frequent and abrupt switches between the power supply grids, as well as low-voltage operating phases of the unidirectional converters. These converters are then strongly biased and the redundant power supply grids are called on more than is strictly necessary. This in particular results in disruptions of the distribution voltage delivered to the electronic equipment situated downstream.
In the second cited document, the power supply system cannot make a prioritized selection of the power supply grids. Furthermore, it is not adapted to filter the inrush currents coming from the equipment situated downstream.